insert an id gotten from another table

Question

I have a message table

**message**
---------------------------------------
msg_id (AI) | user_id | content

and user table

**user**
---------------------------------------
user_id (AI) | email | password | name

I would like to store the user who posted the message into the database. The codes I have written allows me to store the message submitted into the database but not the user_id

if (isset($_POST['submit'])) { // Form has been submitted.
        $msg = new msg();
        $msg->user_id = ???
        $msg->content = trim($_POST['content']);
        if ($msg->createMsg()) {
            //action
        } else {
            //action
        }

the createMsg() is a sql statement that inserts my query.

how do I get the user_id from the user table to store into the message table?

Answer 1

在登录会话期间存储用户数据，如$_SESSION['user'];

$msg->user_id = $_SESSION['user']['user_id'];